1. FIELD OF THE INVENTION:
The present invention relates to apparatus and methods for transferring data between a plurality of data processing, and in particular, the present invention relates to data transfer over a local area network between a plurality of data processing devices.
2. ART BACKGROUND:
It is common to utilize a local area network for the transfer of data and commands between a plurality of data processing devices, such as for example, computer work stations, personal computers, printers, memories and the like. So called "Local Area Networks" (LANS) were developed to connect a collection of computers, work stations, terminals, and other peripheral devices, typically in the same building, and permit each of these devices to communicate with devices attached to other networks. By having different data processing resources perform different tasks, distributed computing provides increased efficiency and power in an overall data processing system. Most local area networks utilize their own high band width cable to permit datagram service between the various devices coupled to the LAN. The most common transmission media for carrier sense local area networks are coaxial cable, twisted pair and fiber optics. A variety of cable topologies are possible using a local area network, such as by way of example, linear, spine, tree, ring and segmented topologies.
In the personal computer market, local area networks have become quite popular as a means for providing distributed processing and communication between personal computers, work stations and other data processing resources. One such local area network is described in U.S. Pat. Nos. 4,689,786, issued August 25, 1987and 4,661,901 , issued April 28, 1987, both owned by Apple Computer, Inc. in Cupertino, California. The local area network disclosed in U.S. Pat. Nos. 4,689,789 and 4,661,902 (hereinafter "the '786 and '902 patents") provide apparatus and methods for transferring data along the local area network between data processing agents. Each agent coupled to the LAN of U.S. Pat. Nos. '786 and '902 follows a protocol for the self assignment of an address on the LAN. This network has become widely used for networking personal computers within office environments and is known as the "Appletalk.TM." network. In practice, Appletalk.TM. operations at a speed of 230.4 kilobits per second.
As will be described, the present invention comprises improved apparatus and methods to boost the speed of communication along a local area network, and in particular, a network of the type disclosed in U.S. Pat. Nos. '786 and '902. Utilizing the teaching of the present invention, the speed of an Appletalk.TM. local area network may be increased by a factor of 3.33. In addition, the present invention provides both high speed, as well as low speed, data communication along a LAN between various types of computers, work stations, printers, disk drives and other data processing agents. The present invention provides a high speed and reliable local area network heretofore unknown in the prior art.